LAUSR

Significance Australopithecus fossils from the richest hominin-bearing deposit (Member 4) at Sterkfontein in South Africa are considerably older than previously argued by some and are contemporary with Australopithecus afarensis in East Africa. Our dates demonstrate the limitations of the widely accepted concept that Australopithecus africanus, which is well represented at Sterkfontein, descended from A. afarensis. The contemporaneity of the two species now suggests that a more complex family tree prevailed early in the human evolutionary process. The dates highlight the limitations of faunal age estimates previously relied upon for the South African sites. They further demonstrate the importance of detailed stratigraphic analysis in assessments of accurate dating of the karst cave sites in South Africa, which are stratigraphically highly complex.